Modern medicine has been indisputably enriched by the intersection of traditional treatments for disease with the inroads of molecular biology. In particular, immunology has provided new hope for the treatment of various diseases, particularly neoplastic diseases, by providing well-characterized and specific antibodies. Antibodies have become important as therapeutic agents because they may be targeted to a specific site for action. For example, cancer cells may possess a “marker” protein that may be a binding site or antigen for a particular antibody.
Historically, antibodies were generated in laboratory animals (usually mice or rabbits) by injecting laboratory animals with the antigen of interest over an extended period. (For general discussion of the structure and biosynthesis of immunoglobulins, see standard immunology textbooks, such as W. E. Paul, Fundamental Immunology, Raven Press, New York, N.Y. 1993, or Janeway et al., Immunobiology The Immune System In Health and Disease, Garland Publishing, New York, N.Y. 2001.) The foreign antigen resulted in an immune response; the resulting antibodies could then be purified from blood. However, this approach has limitations. In vivo use of antibodies from a different species may induce a potentially fatal response (for example, murine antibodies when injected into humans may produce a human anti-mouse antibody response—the “HAMA” response, see, for example, Schiff et al., Cancer Research 45: 879-885 (1985)). Additionally, non-human antibodies will be less efficacious in stimulating human complement or cell mediated toxicity.
Molecular biology again begins to provide an answer to these issues. Chimeric and recombinant antibodies are now being used to address these issues. Chimeric antibodies exploit the component nature of immunoglobulin products by combining portions of antibodies from different species. For example, the variable region from a mouse may be combined with the constant regions from a human. Recombinant DNA techniques are then used for cutting and splicing the various components to form functional immunoglobulin products. Another approach for expanding the utility of antibodies into immunoglobulin products is the technique known as “CDR grafting.” In this method, only the complementarity determining region, “CDR,” is inserted into a human antibody framework. Even this approach may be fine-tuned by substitution of critical murine antibody residues in the human variable regions. The binding of an antibody to its target antigen is mediated through the complementarity-determining regions (CDRs) of its heavy and light chains, with the role of CDR3 of the heavy chain being of particular importance (Xu and Davis, Immunity, 13:37-45, 2000). The use and production of such humanized antibodies continues to be explored, but these techniques are in common current usage. U.S. Pat. Nos. 5,225,539; 5,530,101; 5,585,089; and 5,859,205 describe examples of such techniques.
Yet another approach to avoid the potential problems of immunogenic reactions against non-human protein sequences is using fully human antibodies. Methods for preparing fully human antibodies are well known in the art. For example, fully human antibodies can be prepared by immunizing transgenic mice which express human immunoglobulins instead of mouse immunoglobulins. An antibody response in such a mouse directly generates fully human antibodies. Examples of such mice include the Xenomouse™ (Abgenix, Inc.) and the HuMAb-Mouse@ (Medarex, Inc.), see also U.S. Pat. Nos. 6,207,418, 6,150,584, 6,111,166, 6,075,181, 5,922,545, 5,545,806 and 5,569,825. Antibodies can then be prepared by standard techniques, e.g., standard hybridoma techniques, or by phage display (see below). These antibodies will then contain only fully human amino acid sequences.
Monoclonal antibodies, including fully human antibodies, may also be generated and isolated from phage display libraries. The construction and screening of phage display libraries are well known in the art, see, e.g., Marks et al., J. Mol. Biol. 222(3): 581-597 (1991); Hoogenboom et al., J. Mol. Biol., 227(2): 381-388 (1992); and U.S. Pat. Nos. 5,885,793, and 5,969,108.
The following references are illustrative of such fully human antibodies and phage display techniques: Marks et al., “By-passing immunization. Human antibodies from V-gene libraries displayed on phage,” J. Mol. Biol. 222(3):581-597 (1991); Hoogenboom et al., “By-passing immunisation. Human antibodies from synthetic repertoires of germline VH gene segments rearranged in vitro,” J. Mol. Biol. 227(2):381-388 (1992).
Novel strategies for improving the efficacy of therapeutic monoclonal antibodies, such as augmenting their in vivo effector function, conjugating them directly to cytotoxic agents or radionuclides, and activating such conjugated agents with pre-targeted pro-drugs, as well as coupling monoclonal antibody therapy with traditional chemotherapy regimes, have been introduced. Large scale clinical trials employing these second generation monoclonal antibodies are currently underway and some have gained FDA approval for the treatment of cancer, most notably anti-c-erbB-2/Her2neu (Herceptin) for the treatment of breast cancer, anti-CD20 (Rituxan) for the treatment of non-Hodgkins lymphoma, and anti-CD52 (Campath) for the treatment B cell chronic lymphocytic leukemia.
The discovery of new, therapeutically relevant cell surface target molecules has not kept pace with the rapid advances in monoclonal antibody technology, and only a relatively small number of antigenic targets are being pursued in this regard. This is especially poignant given the momentous progress in gene discovery emanating from the analysis of the human genome, trascriptome, and proteome. In contrast, the identification of intracellular targets for active-specific cancer immunotherapy i.e., cancer vaccines, has flourished in the last decade. Thus, mining the human transcriptome for new cell surface antigens is highly warranted. In this regard, the instant invention resulted partially from searching the human expressed sequence tag (EST) database for novel transcripts encoding tissue-restricted cell surface proteins because these may represent new targets for monoclonal antibody based therapies.
The A33/JAM gene family includes at least seven previously known proteins (A33, CAR, HCTX, ELAM, JAM1, JAM2, and JAM3). These proteins are generally distinguished by two transmembrane domains (with a single signal sequence) and two Ig-like domains. One member, A33, is known to be associated with colon cancer. The isolation and characterization of the A33 molecule is described in U.S. Pat. No. 5,712,369. Humanized antibodies to A33 are described in U.S. Pat. No. 5,958,412; 6,307,026, and Rader et al., J. Biol. Chem. 275(18):13668-76 (2000); methods of using A33 antibodies are described in U.S. Pat. Nos. 6,346,249 B1 and 6,342,587. All these references are specifically incorporated herein by reference.
Human clinical trials have been conducted with mouse and humanized antibodies directed to A33. The biodistribution and imaging characteristics of 131I-mAb A33 were studied in colon carcinoma patients with hepatic metastases. The studies showed that mAb A33 localization was antigen-specific, cancer:liver ratios were 2.3- to 45 fold higher for specific antibody as compared to non-specific antibodies. See, for example, Welt et al., J. Clin. Oncol. 8:1894-1906 (1990). A subsequent radioimmunotherapy phase I/II study of 131I-mAb A33 demonstrated that 131I-mAb A33 had modest anticancer effects in heavily pre-treated patients who were no longer responding to chemotherapy. See, for example, Welt et al., J. Clin. Oncol. 12:1561-1571 (1994).
Other clinical trials and results for A33 mAbs have been described in, for example, Welt et al., “Quantitative analysis of antibody localization in human metastatic colon cancer: a phase I study of monoclonal antibody A33,” J. Clin. Oncol. 8(11):1894-906 (1990); and Welt et al., “Phase I/II study of iodine 131-labeled monoclonal antibody A33 in patients with advanced colon cancer,” J. Clin. Oncol. 12(8):1561-71 (1994).
However, A33 is a marker mainly limited to colon cancer. Two novel members of the A33/JAM family are herein described. One new protein/gene is termed “A34.” Yet another novel member of this family is also described and is termed “A33-like 3.”
U.S. Pat. No. 6,312,921, to Jacobs et al. for “Secreted Proteins and Polynucleotides Encoding Them,” discloses protein and polynucleotides with some overlap with A34. However, these sequences are not identical to A34 or A33-like 3; and, in contrast to the disclosed methods of the instant invention, Jacobs' disclosed uses are non-specific, i.e., for unspecified biological activity, research uses, and nutritional uses.